Different types of line brattices have been used to seal, control and direct the flow of air in underground mines. Those of particular relevance to the present invention are of the extensible curtain type in which at least a portion of the line curtain is advanced toward the mine working face as a material cutting machine advances beyond the last roof bolt of the supported roof.
In mining coal underground, the room and pillar method of mining is often used in which a main gallery has a plurality of rooms or side galleries branching out laterally from the main gallery, separated by pillars. Each pillar is an expanse of rock left unmined in order to prevent subsidence. A mining machine makes a series of cuts into the face of a short wall of a room, as a result of which the room gradually becomes longer.
As material, for example coal, is mined, dust and gases are liberated at the face which, if left to accumulate, could build up to form explosive or otherwise harmful concentrations. Accordingly, ventilation systems have been devised in which escaping gases and/or dust cannot build up but are removed by air channels. In practice, each room is divided by a longitudinal line curtain or brattice which extends from the main gallery to a point near the face, and from the floor to the roof. Typically, the brattice curtain is made of a fire-proofed canvas which is fastened to a batten bolted to the roof and/or fastened to posts. The curtain hangs to the floor where the excess is weighted down with rocks. Typically, the brattice is placed off-center, toward one side of the room. The mining machine is in the wider portion and fans direct a pattern of air circulation carrying dust from the face through the narrower portion provided by division of the room by the brattice curtain. In order to maintain this flow, the brattice curtain must have its leading edge near to but spaced away from the face.
Government regulations require workers to stay away from the face being mined until after the mine roof has been bolted by a cage-protected roof bolting machine operator. The problem to be solved is the manner of extending the brattice curtain, at least temporarily, without any person going into the area where the new section of curtain is to be installed.
Known methods of accomplishing this objective are not entirely satisfactory. Burgess, U.S. Pat. No. 3,715,969 shows a mine ventilation control system including an extensible curtain assembly which is mounted on a header member at mine roof level adjacent the end of a fixed brattice curtain and advanced toward the working face of the mine at a rate commensurate with the removal of the rate of material being mined. Divers, U.S. Pat. No. 4,282,802, shows a slideboard with an attached brattice cloth which acts as an extension of a line brattice. The slideboard is advanced toward the working face of the mine to provide an inlet passage for clean air and an outlet passage for dust-laden air as the mining machine advances. The top of the brattice cloth is supported on half-hoop hoses, providing a flexible seal with the roof of the mine shaft.
The patent to Baker, U.S. Pat. No. 4,440,070, describes a section of brattice mounted on a cart having retractable wheels. The brattice has a frame which permits the curtain section to be extended and retracted vertically for adjustment of height, allowing engagement with the mine roof. The device is spring mounted to enable the top of the curtain to conform to unevenness in the level of the mine roof. The device is bulky and cumbersome in use.
Divers, U.S. Pat. No. 4,494,894, shows a mobile support system for a brattice curtain. The floor engaging member may either be skid plates, wheels, or a conventional roof jack. The curtain depends from an upper support beam which is cantilevered from upwardly extending beams extending from a fulcrum adjacent the floor engaging member. The patent to Hill, U.S. Pat. No. 4,607,507, describes an extensible line brattice including a track system, brattice frame, and a curtain mounted on the track system for extension into an unprotected portion of a mine passage. The track system is engaged midway between the upper and lower edges of the curtain, and the curtain is extended over a frame which terminates at its upper edge adjacent the roof, and at its lower edge adjacent the floor, of the mine shaft.
None of the patents described above shows a readily portable collapsible frame for a brattice curtain which may easily be carried into the mine and pushed out from under the bolted section of a passageway toward the mine face and then extended into working position.